Enable the user to use either a DPDK source tree directory or a
tarball, with and without a pre-built build directory. These can be
stored on either SUT node or the DTS host. The DPDK build setup or the
pre-built binaries can be specified through the configuration file,
the command line arguments or environment variables.

Signed-off-by: Tomáš Ďurovec <tomas.durovec@pantheon.tech>
Signed-off-by: Luca Vizzarro <luca.vizzarro@arm.com>